My armpits randomly started smellin?

I've had this problem for a week or two now. I'm using the same deodorant, soaps, etc. and the same hygiene routine. I'm used to never getting BO at all (in fact I've always been told I smell good), but lately it's been happening just in my armpits. I smell normal everywhere else. Usually I apply deodorant after I shower at night and that lasts me the whole day after, now I reapply maybe 3 times a day. It's not strong enough for other people to notice and it's not like oniony, I smell sort of musky like a man (I'm a 20 year old girl). haha what do I do?